Utility knives, such as are used in the graphic arts, handicrafts, modeling and other diverse applications in homes, factories and offices, have long been known. A standard form of such a utility knife involves a removable, relatively short blade fastened in some means to a shaft or other form of handle.
In one well known version of a utility knife, the blade is fixed to the shaft through a threaded collet. The collet is becomes more tightly held as the collet is screwed int the shaft. In other such knives, all or a portion of the shaft may be hexagonal, rectangular, or knurled, but nearly always straight Perhaps the most famous of such knives are those sold under the X-Acto mark.
Unfortunately, such well-known knives suffer from a number of limitations. Two significant considerations in the design of utility knives having such broad application are control and safety. However, designs of utility knives known in the prior art, while inexpensive, typically provide little consideration to conforming the handle to the hand in a manner which imparts such control and safety.
Most particularly, the simple, straight shaft, often as small as a pencil, of the prior art utility knife can rotate away from the object, creating a loss of control that increases risk of injury to the user as well risk of damage to the object.
Additionally, the typical collet lock of the prior art frequently binds on the blade, forcing the user seeking to change blades to tug or otherwise directly contact the blade to force it out of the collet. Alternative designs are also known in the prior art which maintain angles and friction such that the collet is intended to ride freely in its sleeve, but these designs have been found unreliable because friction between materials may vary widely with changes in operating conditions that may be encountered over the useful life of the knife.
These and other limitations of the prior art have established a need for a simple, inexpensive, easy to control and relatively safe utility knife.